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Bike misses and stumbles

I'll step out of my box here, and act like I know what I'm talking about. When you start her up again after a short run, does she idle just a smidge higher?

Does she starts missing and sputtering in 4 and 5? After she starts sputtering, does she do it in all gears?

These are the same symptoms I had.

Just for grins, check your throttle body shaft. May be cracked. It was a booger seeing mine. It's the shaft that keeps the "butterfly" in place on your intake. After it happened to me, I see its not unusual for our older scoots.

Bubbles? They don't belong in a tank. Are you sure about those lines? Get to a half tank. Take the cap off , hit the run switch. Stick your ear by the opening of the tank. If you hear fuel splashing, you have a hole.

Good luck. Keep us posted. You're helping quite a few on here.
 
Mine was cracked right behind the bracket. Couldn't see it. The only way we found it was when we checked the tps sensor (?) #15 in post 21. When we checked that, the shaft came out with it. Thus discovering the break. I could slide it back in and duplicate the symptoms. Remedy - New throttle body.

Now keep in mind, I'm just throwing a thought out there. My experience with scoots is based solely on my own. Hang in there, these guys on here will get you up and rolling before we start griping it's too hot to ride. :D
 
ddickerson said:
Could this be a ECM problem?
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Absolutely. If you have a buddy that will allow you to try his ECM, that would be the way to check; plug it in and go for a ride. IIRC, a new ECM will run about $275 from an online discount dealer.
 
An update on what I have tried. Pulled TPS shaft to throttle body seems fine, checked injectors both reading 14.3 ohms, wiggled plug wires with a meter and no break in continuity. Battery reads 12.5 volts, pulled supply hose out of tank can't find any holes.

I do not know anyone that I can swap ECM for a test.

Which online discount dealer do you use?

HD said they occasionally screw the two screws at the top of the throttle body in to make the bike run richer, anyone familiar with this? When the bike start to cut out it's much worse than a miss, now seems that I am losing a cylinder!
 
ddickerson said:
An update on what I have tried. Pulled TPS shaft to throttle body seems fine, checked injectors both reading 14.3 ohms, wiggled plug wires with a meter and no break in continuity. Battery reads 12.5 volts, pulled supply hose out of tank can't find any holes.

I do not know anyone that I can swap ECM for a test.

Which online discount dealer do you use?

HD said they occasionally screw the two screws at the top of the throttle body in to make the bike run richer, anyone familiar with this? When the bike start to cut out it's much worse than a miss, now seems that I am losing a cylinder!
Click to expand...

Not familiar with the MM throttle body but I wouldn't mess with those two screws as they are most likely not the source of your problem.

There are several online discount dealers; Ronnies, Lakeside, Surdyke and New Castle (used to be Zanotti's). I have found New Castle to be consistently a bit more economical when shipping cost is included.

I wish you could find someone that would let you plug in their ECM before you spend an additional $300 only to find that it doesn't solve the problem. However, it seems that you have checked CPS, TPS, fuel delivery, injector function/connection and I am not sure what else there is to check. However, I know when a problem like this makes a bike unrideable, throwing money and parts at a problem with fingers crossed is on approach when all others have failed.:bigsmiley21:
 
Just something to think about and may not have anything to do with your problem, but a full charged battery should be 12.7. Have you done a load test on the battery?
 
ddickerson said:
Changed CKP last night, weather permitting I will test ride after work.
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CKP = CPS = crank position sensor which I thought you had checked already. I suppose it could be the CPS going bad but you have never indicated that there was a starting issue which is usually a symptom of a CPS going out. I hope that solves the problem for you; sometimes they just need cleaning.:s

Have you not tried to pull codes from the ECM? Seems to me that would be the first order of business.:coffee
 
As you said the original owner changed the CKP a few years ago but it still may be the culprit. Hope this works!

Also a clarification, in my post # 50 I said "vacuum line on the regulator at the M-M induction"......I don't know where I came up with that, maybe I dreamed that??? my bad.
 
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